Clothing dryer and method of controlling the same

ABSTRACT

Disclosed herein is a dryer which includes a drum for accommodating an object to be dried, a combustion device for combusting gas to heat air, a blowing device for transferring the heated air into the drum, and a valve assembly for controlling a gas discharge amount supplied to the combustion device, wherein the valve assembly may operate in one mode among a high heating power mode which maximizes the gas discharge amount, a low heating power mode which generates 50% or less heating power compared to the high heating power mode, and a standby mode which blocks the gas discharge.

CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY

The present application is related to and claims the benefit of KoreanPatent Application No. 10-2015-0014737, filed on Jan. 30, 2015 in theKorean Intellectual Property Office, the disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a clothing dryer which dries an objectto be dried and a method of controlling the same.

BACKGROUND

Generally, a clothing dryer is an apparatus which rotates a drying drum,in which wet clothing is accommodated, at a low speed and allowshigh-temperature air to pass through the drying drum and flow in thedrying drum in order to dry the clothing in the drying drum. The dryermay be classified as an exhaust type dryer which exhaustshigh-temperature, humid air that has passed through the drying drum outof the dryer, and a condensation type dryer which removes moisture fromhigh-temperature, humid air that has passed through the drying drum andcirculates the air back into the drying drum. Also, the dryer may beclassified as an electric drier and a gas type dryer according to amethod of heating air, such as a heating means. The electric dryer heatsair using electrical resistance heat, and the gas type dryer heats airusing heat generated by combustion of gas. However, the gas type dryeris capable of controlling heating power. The dryer may be classified asthe electric drier and the gas type dryer according to the method ofheating air, such as a heating means. The electric dryer heats air usingelectrical resistance heat, and the gas type dryer heats air using heatgenerated by combustion of gas.

SUMMARY

To address the above-discussed deficiencies, it is a primary object toprovide, for use in a dryer capable of efficiently controlling heatingpower and a method of controlling the same.

According to an aspect, a dryer includes a drum for accommodating anobject to be dried, a combustion device for combusting gas to heat air,a blowing device for transferring the heated air into the drum, and avalve assembly for controlling a gas discharge amount supplied to thecombustion device, wherein the valve assembly may operate in one modeamong a high heating power mode which maximizes the gas dischargeamount, a low heating power mode which generates 50% or less heatingpower compared to the high heating power mode, and a standby mode whichblocks the gas discharge. Here, the low heating power mode may generate30% heating power compared to the high heating power mode.

In addition, the valve assembly may further include an output controlvalve for closing a gas flow passage to decrease an open rate. Inaddition, the dryer may further include a dryness sensor for detecting adryness level of an object to be dried, and a control unit for comparingthe dryness level detected from the dryness sensor to a referencedryness level in order to control the valve assembly such that theoperation mode of the valve assembly is changed. Here, the control unitmay control the valve assembly to operate alternately between the highheating power mode and the low heating power mode. In addition, thedryer may further include a temperature sensor for measuring atemperature of air which flows into the drum, and a control unit forcomparing the temperature measured from the temperature sensor to areference temperature in order to control the valve assembly such thatthe operation mode of the valve assembly is changed. Here, the controlunit may control the valve assembly to operate alternately between thehigh heating power mode and the low heating power mode.

The dryer may further include a dryness sensor for detecting a drynesslevel of an object to be dried, and determine a maintenance time of thehigh heating power mode based on the dryness level change rate detectedfrom the dryness sensor. In addition, the combustion device may furtherinclude an igniter for igniting gas, and a control unit for controllingthe valve assembly to operate in the high heating power mode when theigniter operates. In addition, the valve assembly may further include asafety valve for determining whether to discharge gas or not. Inaddition, the control unit may control the safety valve to be openedwhen the temperature of the igniter reaches an ignition point of gas.According to another aspect, a clothing dryer includes a control unitfor controlling an operation, a drum for accommodating an object to bedried, a valve assembly capable controlling heating power by controllinga gas discharge amount, a combustion device for combusting the gasdischarged from the valve assembly to generate hot air, and a blowingdevice for transferring the hot air into the drum. Here, the valveassembly may further include an output control valve for decreasing anopen rate of the valve assembly to a predetermined open rate in order tocontrol the gas discharge amount.

In addition, the clothing dryer may further include a dryness levelmeasurement unit for measuring a dryness level of the object to bedried, and the output control valve may decrease the open rate of thevalve assembly to be low until the dryness level of the object to bedried reaches a preset reference dryness level. In addition, the outputcontrol valve may decrease the open rate of the valve assembly for areference time in which a dryness level of the object to be dried ispreset. In addition, the valve assembly may further include a safetyvalve for determining whether to discharge gas or not.

According to another aspect, a method of controlling a clothing dryerwhich includes a combustion device in which heating power is controlledby a valve assembly which controls a gas discharge amount in accordancewith a plurality of predetermined open rates may include controlling thevalve assembly to a low open rate among the plurality of open rates todry an object to be dried in a low heating power mode and, when thedryness level of the object to be dried reaches a preset referencedryness level, controlling the valve assembly to a high open rate amongthe plurality of open rates to dry an object to be dried in a highheating power mode.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 is a perspective view illustrating an exterior of a clothingdryer according to an embodiment;

FIG. 2 is a schematic cross-sectional view of the clothing dryeraccording to an embodiment;

FIG. 3 is a view schematically illustrating a front support plate of theclothing dryer according to an embodiment;

FIG. 4 is a view illustrating in detail a guide member of the clothingdryer according to an embodiment;

FIG. 5 is a view schematically illustrating a combustion device of theclothing dryer according to an embodiment;

FIG. 6 is a view illustrating another embodiment of an igniter of theclothing dryer according to an embodiment;

FIG. 7 is a view for describing a gas supply of a valve assembly;

FIG. 8 is an exploded perspective view of the valve assembly fordescribing an embodiment of an output control valve;

FIG. 9 is a control block diagram for describing in detail an operationof the clothing dryer according to an embodiment;

FIG. 10 is a view illustrating a pulse generation frequency of a drynesslevel detector in accordance with time according to an embodiment;

FIG. 11 is a view for describing a combustion device operation unit ofthe clothing dryer according to an embodiment;

FIG. 12 is a view for describing an operation at the time of ignition ofthe combustion device operation unit in FIG. 11;

FIG. 13 is a flow chart for describing an embodiment of a method ofcontrolling the clothing dryer according to an embodiment;

FIG. 14 is a view for describing an air flow in a drying process of theclothing dryer according to an embodiment;

FIG. 15 is a flow chart for describing an embodiment of an ignitionprocess in FIG. 10;

FIG. 16 is a view illustrating a temperature change in air when exhaustblockage has occurred;

FIG. 17 is a view for describing an embodiment of a re-ignition process;

FIG. 18 is a flow chart for describing in detail an embodiment of adrying process in FIG. 13;

FIG. 19 is a graph illustrating a change in open rates in the dryingprocess of FIG. 18;

FIG. 20 is a flow chart for describing in detail another embodiment ofthe drying process in FIG. 13;

FIG. 21 is a flow chart for describing in detail still anotherembodiment of the drying process in FIG. 13;

FIG. 22 is a view for describing another embodiment of a mode change inthe drying process;

FIG. 23 is a view for describing a control for tracking a temperature;

FIG. 24 is a view for describing a drying process which limits an outputbased on the temperature;

FIG. 25 is a flow chart for describing an embodiment of analyzingcharacteristics of an object to be dried; and

FIG. 26 is a view for describing a change in dryness level in accordancewith characteristics of an object to be dried.

DETAILED DESCRIPTION

FIGS. 1 through 26, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged clothing dryer or other dryingdevice. Hereinafter, a clothing dryer and a method of controlling thesame will be described in detail with reference to the accompanyingdrawings.

FIG. 1 is a perspective view illustrating an exterior of a clothingdryer according to an embodiment, and FIG. 2 is a schematiccross-sectional view of the clothing dryer according to an embodiment.Referring to FIGS. 1 and 2, a clothing dryer 1 according to anembodiment may include a housing 10 forming the exterior, a drum 20rotatably installed within the housing 10, a hot air supply unit 40supplying hot air into the drum 20, a hot air discharge unit 50 throughwhich the air that has dried an object to be dried in the drum 20 isdischarged, a combustion device 100 heating the air, and a circulationdevice circulating the heated air to generate hot air.

The housing 10 forms the exterior of the clothing dryer 1. A controlpanel 230 for controlling the clothing dryer 1 may be provided at a topside of a front surface of the housing 10. Also, an inlet 11 forinserting or withdrawing an object to be dried into or from the drum 20is formed at the front surface of the housing 10. In addition, a door 15is coupled to the front surface of the housing 10 by a hinge. The door15 is provided in a shape corresponding to the inlet 11. A user may openthe door 15 by rotating the door 15 forward, and insert or withdraw theobject to be dried into or from the drum 20. Also, the door 15 may berotated toward the clothing dryer 1 to close the drum 20.

In addition, a plurality of through-holes 17 may be provided at thehousing 10. Outside air may be introduced into the clothing dryer 1through the through-holes 17. As illustrated in FIG. 1, thethrough-holes 17 may be provided at a lower portion of the front surfaceand a side surface of the housing 10. Also, as illustrated in FIG. 2,the through-holes 17 may be provided at a rear surface of the housing10. The drum 20 is rotatably installed within the housing 10. The drum20 may include a cylindrical portion 21, a front support plate 22, and arear support plate 23. The cylindrical portion 21 is formed in acylindrical shape with open front and rear surfaces, the front supportplate 22 is coupled to the front surface of the cylindrical portion 21,and the rear support plate 23 is coupled to the rear surface thereof.

Here, the inlet 11 for inserting or withdrawing the object to be driedis formed at the front support plate 22, and a plurality of lifts 24 maybe provided inside the cylindrical portion 21 along a circumferentialdirection. The object to be dried inside the drum 20 is lifted andlowered repetitively by the lifts 24. That is, the lifts 24 lift andlower the object to be dried, thus allowing the object to be dried to beeffectively dried. In addition, rollers 30 for supporting the drum 20are provided at lower ends of an outer circumferential surface of thedrum 20. The rollers 30 may rotatably support the drum 20 by beingprovided at front and rear lower ends, respectively, of the outercircumferential surface of the drum 20. Here, the rollers 30 may befixed by the front support plate 22 and the rear support plate 23,respectively.

The hot air supply unit 40 supplies high-temperature, dry hot air to thedrum 20. The hot air supplied to the drum 20 absorbs moisture of theobject to be dried inside the drum 20. Specifically, the hot air supplyunit 40 may include a combustion chamber 41 in which air is heated bythe combustion device 100, a bottom duct 42 for guiding the heated airto a rear duct 43, the rear duct 43 for guiding the heated air to a hotair outlet 45, and the hot air outlet 45 through which the hot air isdischarged into the drum 20. Air in the combustion chamber 41 is heatedby the combustion device 100 to be described below. The combustionchamber 41 may be provided in a hollow conical shape in which a rear endhas a smaller diameter than a front end.

Air may be introduced through the front end of the combustion chamber41, and the air introduced through the front end of the combustionchamber 41 is heated by the combustion device 100. A rear end of thecombustion chamber 41 is coupled to the bottom duct 42. The combustionchamber 41 may be coupled to the bottom duct 42 by being insertedtherein. For this, the diameter of the bottom duct 42 may be provided tobe larger than the diameter of the rear end of the combustion chamber41. In addition, due to the difference between the diameter of the rearend of the combustion chamber 41 and the diameter of the bottom duct 42,air outside the combustion chamber 41 may be introduced into the bottomduct 42.

The air heated in the combustion chamber 41 is guided to the hot airoutlet 45 through the bottom duct 42 and the rear duct 43. The rear duct43 is provided to be a predetermined distance apart from the rearsupport plate 23, thus forming a rear flow passage 44 through which airmay move. Meanwhile, a gas sensor 133 for detecting a gas leak may beprovided at one side of the combustion chamber 41. The gas sensor 133detects whether gas is leaked or not. When a gas leak is detected, theclothing dryer 1 controls a valve assembly (120 in FIG. 6) to preventgas from being discharged to a mixing tube (131 in FIG. 6). The gassensor 133 may be implemented using a catalytic combustion sensor, asemiconductor sensor, a ceramic sensor etc., but is not limited thereto.

The hot air outlet 45 may be provided at an upper end of the rearsupport plate 23. The heated air that has moved along the bottom duct 42and the rear duct 43 is introduced into the drum 20 through the hot airoutlet 45, thus absorbing moisture of an object to be dried inside thedrum 20. A first temperature sensor 49 may be provided at the rear duct43. The first temperature sensor 49 detects a temperature of air guidedinto the drum 20 through the rear flow passage 44. Here, the firsttemperature sensor 49 may be implemented using a catalytic temperaturesensor or a non-catalytic temperature sensor. Specifically, thetemperature sensor may be implemented using at least one of a resistancetemperature detector (RTD) temperature sensor which uses a change inresistance of a metal in accordance with a change in temperature, athermistor temperature sensor which uses a change in resistance of asemiconductor in accordance with a change in temperature, a thermocoupletemperature sensor which uses an electromotive force generated at bothends of a junction point of two types of metallic lines formed ofdifferent materials, and an IC temperature sensor which uses voltages atboth ends of a transistor changing in accordance with a temperature orcurrent and voltage characteristics of a P-N junction portion. However,the temperature sensor is not limited thereto and may employ allpossible means for detecting a temperature.

In addition, although the first temperature sensor 49 is illustrated inFIG. 2 as being provided at an upper portion of the rear duct 43, theposition of the first temperature sensor 49 is not limited thereto. Forexample, the first temperature sensor 49 may be disposed at a lowerportion of the rear duct 43, the bottom duct 42, or the hot air outlet45. The hot air discharge unit 50 guides the discharge of air in thedrum 20. The high-temperature, dry air introduced into the drum 20through the hot air outlet 45 changes to a low-temperature, humid air asthe air absorbs moisture of the object to be dried. The low-temperature,humid air may be discharged to the outside through the hot air dischargeunit 50. The hot air discharge unit 50 may be provided at a lower end ofthe front support plate 22. FIG. 3 is a view schematically illustratinga front support plate of the clothing dryer according to an embodiment.FIG. 4 is a view illustrating in detail a guide member of the clothingdryer according to an embodiment. Referring to FIGS. 2 to 4, the hot airdischarge unit 50 may include a guide member 51 for guiding anintroduction of air in the drum 20 into a front flow passage 53, and afront duct 54 which forms the front flow passage 53. The front flowpassage 53 may be formed by the front duct 54 provided at a lowerportion of a front surface of the clothing dryer 1.

The guide member 51 may be provided at a lower side of the front supportplate 22 to guide the introduction of the air in the drum 20 into thefront flow passage 53. A plurality of air inlets 52 may be provided atthe guide member 51, and the air in the drum 20 may be guided to thefront flow passage 53 through the plurality of air inlets 52. A filtermember 55 filters foreign substances such as dust or lint included inthe air introduced into the front flow passage 53. A handle 56 whichfacilitates detachment of the filter member 55 may be provided above thefilter member 55.

A blowing device 60 circulates air in the clothing dryer 1. The blowingdevice 60 includes a fan casing 61, a blowing fan 62 provided in the fancasing 61, and a driving motor 63 which rotates the blowing fan 62. Afront end of the fan casing 61 is connected to the front flow passage53, and a rear end of the fan casing is connected to an exhaust duct 67.The driving motor 63 has a driving shaft extending forward and connectedto the blowing fan 62. Thus, the blowing fan 62 may rotate by thedriving motor 63. Also, the driving shaft of the driving motor 63 mayextend backward and be connected to a pulley 64 for driving the drum 20.Since the pulley 64 and the drum 20 are connected by a belt 65, the drum20 may rotate by rotation of the driving motor 63. That is, the drum 20and the blowing fan 62 may rotate at the same time by the driving motor63.

The blowing fan 62 rotates inside the fan casing 61 to generate an airflow inside the clothing dryer 1. The air in the front flow passage 53is discharged out of the clothing dryer 1 through the exhaust duct 67 bythe rotation of the blowing fan 62. When the air in the front flowpassage 53 is discharged through the exhaust duct 67, the pressure inthe front flow passage 53 decreases, and air in the drum 20 moves intothe front flow passage 53. Also, the introduction of air heated by thecombustion device 100 increases when the pressure of the air in the drum20 decreases. That is, a supply of heated air from the hot air supplyunit 40 is facilitated when the blowing fan 62 rotates.

Meanwhile, a sensor mounting unit 58 on which a dryness level detectionunit 210 is mounted may be provided at the guide member 51. Here, thedryness level detection unit 210 is an element that generates anelectrical signal in accordance with the amount of moisture contained inan object to be dried. The dryness level detection unit 210 will bedescribed in detail herein.

A second temperature sensor 59 may be provided at the front duct 54. Thesecond temperature sensor 59 detects a temperature of air guided to thefront duct 54. Here, the second temperature sensor 59 may be implementedusing a catalytic temperature sensor or a non-catalytic temperaturesensor. In addition, although the second temperature sensor 59 isillustrated in FIG. 2 as being provided at the front duct 54, theposition of the second temperature sensor 59 is not limited thereto. Forexample, the second temperature sensor 59 may be provided at one surfaceof an inside of the guide member 51.

The combustion device 100 heats air to generate hot air. Here, a heatingpower of the combustion device 100 may be controlled to control thetemperature of the hot air. The heating power increases when a greatamount of gas is combusted, and the temperature of the hot air increaseswhen the heating power increases. The heating power decreases when asmall amount of gas is combusted, and the temperature of the hot airdecreases when the heating power decreases. The heating power of thecombustion device 100 may be controlled in multiple stages. For example,the combustion device 100 may be controlled to be one operation modeamong a high heating power mode, a low heating power mode, and a standbymode. The high heating power mode refers to a state in which the gasdischarge amount is the maximum, and is a mode having the highestheating power. The low heating power mode refers to a state in which asmaller amount of gas is discharged compared to the gas discharge amountin the high heating power mode, and is a mode having a heating powerlower than that in the high heating power mode, such as 50% or lessheating power compared to that in the high heating power mode. Thestandby mode refers to a state in which the gas discharge is blocked andgas is not combusted in the combustion device 100.

Since the mode of the combustion device 100 changes in accordance withthe amount of gas discharged to the combustion device 100, the mode ofthe combustion device 100 may be determined by the valve assembly 120which controls the amount of gas discharged to the combustion device100. Hereinafter, each configuration of the combustion device 100 willbe described in detail.

FIG. 5 is a view schematically illustrating a combustion device of theclothing dryer according to an embodiment. FIG. 6 is a view illustratinganother embodiment of an igniter of a combustion device 100 a of theclothing dryer according to an embodiment. FIG. 7 is a view fordescribing a gas supply of a valve assembly. FIG. 8 is an explodedperspective view of the valve assembly 120 for describing an embodimentof an output control valve. Referring to FIGS. 5 to 8, the combustiondevice 100 may include a valve support 110, the valve assembly 120 fordischarging gas, and a combustion unit 130 for combusting gas. The valvesupport 110 is coupled to the valve assembly 120 to support the valveassembly 120. The valve support 110 includes a first support 111extending from one end of the valve support 110 to support the valveassembly 120, and a second support 115 extending from the one end of thevalve support 110 to support the other end of the valve assembly 120.

The first support 111 and the second support 115 may respectivelyinclude inclined surfaces 112 and 116 extending from one end of thevalve support 110 and vertically bent to be parallel to a gas injectiondirection. The second support 115 extends in a shorter length comparedto the first support 111, and the inclined surface 116 of the secondsupport 115 is positioned at a lower side than the inclined surface 112of the first support 111. The valve support 110 and the valve assembly120 may be coupled by screws. For the screw coupling, screw fasteningholes 113 and 117 may be formed at the inclined surface 112 of the firstsupport 111 and the inclined surface 116 of the second support 115, andscrew fastening holes may also be formed at the valve assembly 120 atpositions corresponding to the screw fastening holes 113 and 117 of thevalve support 110.

The valve assembly 120 may control the discharge amount of gas tocontrol the heating power of the combustion device 100. The valveassembly 120 may control the gas discharge amount in multiple stages inaccordance with the operation modes. Specifically, the valve assembly120 may maximize the gas discharge amount in the high heating powermode, decrease the gas discharge amount such that the heating power is50% or less compared to the high heating power mode in the low heatingpower mode, and block the gas discharge in the standby mode. The gasdischarge amount of the valve assembly 120 in accordance with theoperation modes is controlled in accordance with the open rate of thevalve assembly 120. The open rate is an index which shows an extent towhich the valve is open. For example, the open rate is 100% when thevalve is completely open, and the open rate is 0% when the valve isclosed.

That is, the gas discharge amount increases and the heating powerincreases as the open rate of the valve assembly 120 is higher, and thegas discharge amount decreases and the heating power decreases as theopen rate of the valve assembly 120 is lower. The open rate of the valveassembly 120 may be set as one of a plurality of predetermined openrates. For example, the open rate of the valve assembly 120 may be setas one of 100%, 30%, and 0%. When the valve assembly 120 has the aboveopen rates, the open rate may be 100% in the high heating power mode,30% in the low heating power mode, and 0% in the standby mode.Specifically, the valve assembly 120 may include a decompressor 122, aplurality of safety valves 123 and 124, and an output control valve 125.

The valve assembly 120 receives gas through a gas inlet 121. The gasinlet 121 is connected to a gas tube 140 to which gas is guided from agas supply source outside the housing 10. The decompressor 122 controlsthe pressure of the gas introduced through the gas inlet 121. Since thepressure of the gas introduced through the gas inlet 121 is high, thepressure of the gas needs to be lowered to a pressure suitable forcombustion. The decompressor 122 decreases the pressure of the gassupplied through the gas inlet 121. The gas, whose pressure is loweredby the decompressor 122, is applied to the output control valve 125. Theplurality of safety valves 123 and 124 may control whether the gas isdischarged or not. That is, the gas is discharged only when both of afirst safety valve 123 and a second safety valve 124 are open. Thecombustion device 100 with the plurality of safety valves 123 and 124 isprovided, such that an accident due to a gas leak may be prevented.

The output control valve 125 may be provided between the first safetyvalve 123 and the decompressor 122. The output control valve 125 maycontrol the open rate of the valve assembly 120. That is, the outputcontrol valve 125 may control the heating power of the combustion device100. Since the gas discharge amount of the valve assembly 120 iscontrolled in accordance with the open rate, and the heating power iscontrolled in accordance with the gas discharge amount as mentionedabove, the output control device may control the open rate of the valveto control the heating power of the combustion device 100. The outputcontrol valve 125 may be implemented using a solenoid valve.Hereinafter, an embodiment of the output control valve 125 will bedescribed in detail with reference to FIG. 8. The output control valve125 is formed of an orifice 125 b and a valve body 125 a. A coil isprovided in the valve body 125 a. A magnetic field is formed whencurrent flows through the coil in the valve body 125 a, and the orifice125 b may move by the magnetic field.

The orifice 125 b may move back and forth along an axis parallel to agas flow passage 129. Specifically, the orifice 125 b moves forwardtoward the gas flow passage 129 when the magnetic field is formed in thevalve body 125 a, and the orifice 125 b moves backward toward the valvebody 125 a when the magnetic field is not formed in the valve body 125a. When the orifice 125 b is positioned in the valve body 125 a, the gasflow passage 129 is completely open and has a high first open rate (suchas 100%). However, when the orifice 125 b moves forward toward the gasflow passage 129, the gas flow passage 129 is closed by the orifice 125b. In addition, gas moves along an inner flow passage 125 c in theorifice 125 b. That is, the gas flow passage 129 is closed by theorifice 125 b, causing the open rate of the gas flow passage 129 to belowered to a second open rate (such as 30%). When the open rate islowered from the first open rate to the second open rate by the orifice125 b, the amount of gas discharged to the combustion unit 130 reduces,such that the heating power of the combustion device 100 decreases.

In other words, the output control valve 125 decreases the open rate ofthe gas flow passage 129 to a predetermined second open rate. Here, thepredetermined second open rate may be determined according to the sizeand structure of the orifice 125 b. For example, the second open ratemay be determined according to the size of the inner flow passage 125 cformed in the orifice 125 b. The clothing dryer 1 may control the outputcontrol valve 125 to control the heating power mode. Specifically, theclothing dryer 1 may control back and forth motions of the orifice 125 bof the output control valve 125 to control the operation mode. In otherwords, since the gas flow passage 129 is completely open when theorifice 125 b moves forward, the gas discharge amount of the combustiondevice 100 becomes the maximum, and the combustion device 100 operatesin the high heating power mode.

Since the gas flow passage 129 is partially closed when the orifice 125b moves backward, the gas discharge amount of the combustion device 100decreases, and the combustion device 100 operates in the low heatingpower mode. As described herein, since the heating power may becontrolled by controlling the back and forth motions of the orifice 125b, the combustion device 100 may control the heating power withoutrepeating extinction and ignition. Meanwhile, when all of the safetyvalves are open, the gas may be discharged through a gas outlet 126.Here, a front end portion of the mixing tube 131 may be positioned inthe combustion chamber 41. The gas discharged through the gas outlet 126is mixed with air in the mixing tube 131. An igniter 132 may be providedat the front end portion of the mixing tube 131. The igniter 132 ignitesthe gas mixed with air. The ignited gas heats surrounding air whilebeing continuously combusted with air.

The igniter 132 applies a temperature higher than the ignition point ofgas to ignite the gas mixed with air. The igniter 132 may be a heatedtype igniter 132 which is heated up to a temperature greater than theignition point of the gas as illustrated in FIG. 5, but is not limitedthereto. For example, the igniter 132 may be implemented using anignition plug 132 a which generates and ignites electric flames asillustrated in FIG. 6. The operation of the clothing dryer 1 isdescribed in detail herein.

FIG. 9 is a control block diagram for describing in detail an operationof the clothing dryer according to an embodiment. Referring to FIG. 9,the clothing dryer 1 may include the dryness level detection unit 210for detecting the dryness level of an object to be dried, a statedetection unit 220 for detecting a state of the clothing dryer 1, thecontrol panel 230 for receiving a control command from a user andproviding information to the user, a storage unit 240 for storing datato operate the clothing dryer 1, and a control unit 270 for controllingthe overall operation of the clothing dryer 1. The dryness leveldetection unit 210 may detect the dryness level of an object to bedried. The dryness level detection unit 210 may be installed in the drum20 and come in contact with the object to be dried which rotates in thedrum 20 in order to detect the dryness level of the object to be dried.Here, the dryness level is an index which shows an extent to which themoisture included in the object to be dried is dried. A higher drynesslevel signifies that a greater amount of moisture is included in theobject to be dried, and a lower dryness level signifies that a lesseramount of moisture is included in the object to be dried. Hereinafter,an embodiment of the dryness level detection unit 210 will be describedwith reference to FIGS. 3 and 4.

Referring to FIGS. 3 and 4, the dryness level detection unit 210 mayinclude a first electrode 211 and a second electrode 212. The firstelectrode 211 and the second electrode 212 may be provided at the guidemember 51. The first electrode 211 and the second electrode 212 aremounted on the sensor mounting unit 58 provided at the guide member 51.The first electrode 211 and the second electrode 212 may be provided tobe curved in accordance with the shape of the sensor mounting unit 58.The first electrode 211 and the second electrode 212 may be mounted onthe sensor mounting unit 58 formed at the guide member 51 while beingspaced apart from each other. Since the first electrode 211 and thesecond electrode 212 are provided to be a predetermined distance apartfrom each other, the first electrode 211 and the second electrode 212remain electrically open to each other.

When an object to be dried which has moisture comes in contact with thefirst electrode 211 and the second electrode 212 at the same time, thefirst electrode 211 and the second electrode 212 are shorted by themoisture included in the object to be dried, causing current to flowbetween the first electrode 211 and the second electrode 212. That is, acurrent pulse is generated at the first electrode 211 and the secondelectrode 212 by the object to be dried which has moisture. Thus, thedryness level detection unit 210 may detect the dryness level of theobject to be dried based on the current pulse generated by the moistureof the object to be dried. FIG. 10 is a view illustrating a pulsegeneration frequency in accordance with time of a dryness level detectoraccording to an embodiment.

When the clothing dryer 1 operates, the frequency of the current pulsegenerated at the first electrode 211 and the second electrode 212 maychange as illustrated in FIG. 10. The object to be dried has highdryness level at an early stage of drying. Thus, the current pulse isfrequently generated by the object to be dried when the drum 20 beginsrotating, and the frequency of the current pulse generation is also highas illustrated in FIG. 10. Meanwhile, humidity of the object to be driedgradually decreases as the object to be dried is dried by the hot air.Thus, as the object to be dried is dried, the frequency of the currentpulse generation gradually decreases as illustrated in FIG. 10.

In other words, the dryness level detection unit 210 may detect a changein the dryness level of the object to be dried based on the frequency ofthe current pulse generation. Since the moisture content in the objectto be dried is high when the dryness level is low, a current flowfrequently occurs between the first electrode 211 and the secondelectrode 212, such that the frequency of the current pulse generationis high. Since the frequency of the current flow generation between thefirst electrode 211 and the second electrode 212 decreases when theobject to be dried is dried and the dryness level thereof is lowered,the frequency of the current pulse generation decreases. Although thefirst electrode 211 and the second electrode 212 of the dryness leveldetection unit 210 have been described as being provided at the guidemember 51, the position of the dryness level detection unit 210 is notlimited thereto.

In addition, although the first electrode 211 and the second electrode212 are illustrated as having curved shapes in FIGS. 3 and 4, the shapesof the first electrode 211 and the second electrode 212 are not limitedthereto. For example, the first electrode 211 and the second electrode212 may be formed in the shape of a rod. The state detection unit 220may detect the state of the clothing dryer 1. Here, the state of theclothing dryer 1 refers to various types of information such as atemperature of air in the clothing dryer 1 and a gas ignition state tooperate the clothing dryer 1. The state detection unit 220 may include atemperature sensor for detecting the temperature of air, the gas sensor133 for detecting a gas leak, etc. Specifically, the state detectionunit 220 may detect the temperature of air introduced into the drum 20using the first temperature sensor 49 and detect the temperature of airdischarged from the drum 20 using the second temperature sensor 59.

In addition, the state detection unit 220 may detect whether gas isleaked or not based on the gas sensor 133. For example, the gas sensor133 may be provided in the combustion chamber 41 as a catalyticcombustion sensor as illustrated in FIG. 2 to detect the temperature inthe combustion chamber 41. When the temperature in the combustionchamber 41 detected by the catalytic combustion sensor is lower than apreset temperature even though gas is being discharged to the combustionchamber 41, the state detection unit 220 may detect that gas is leaking.The control panel 230 may receive a control command from a user orprovide information related to the operation of the clothing dryer 1 tothe user. The control panel 230 may be provided at an upper side of thefront surface of the clothing dryer 1 as illustrated in FIG. 1 to beeasily manipulated by the user.

Specifically, the control panel 230 may include an input unit 231 whichreceives a control command from the user. The user may select one dryingcourse among a plurality of preset drying courses through the input unit231. The drying courses may be classified in accordance with the type,weight, etc., of the object to be dried. Also, the drying courses may beclassified in accordance with energy efficiency or a target drynesslevel. Here, the target dryness level refers to the final dryness levelof the object to be dried after drying is ended. The moisture contentincluded in the object to be dried that has reached the target drynesslevel is low.

The input unit 231 may be implemented using devices such as a touchsensor, a push button, a membrane button, a dial, and a slider switch.Here, the touch sensor is a device which detects a touch input of auser, and an electrostatic capacitive technology, a resistance typetechnology, an infrared ray technology, and a surface acoustic wavetechnology may be used for the touch sensor, but the technologies arenot limited thereto. In addition, the control panel 230 may include adisplay unit 232 for displaying information to the user. The displayunit 232 may display a state of the clothing dryer 1 or a time remaininguntil drying is finished. The display unit 232 may be implemented usingdisplay means such as a plasma display panel, a liquid crystal displaypanel, a light-emitting diode panel, an organic light-emitting diodepanel, or an active organic light-emitting diode panel, but is notlimited thereto.

The storage unit 240 stores various types of data for the operation ofthe clothing dryer 1. For example, the storage unit 240 may storefirmware or various types of applications for the operation of theclothing dryer 1. In addition, a drying algorithm may be stored in thestorage unit 240. The drying algorithm is related to a procedure fordrying an object to be dried. A proper drying procedure differs inaccordance with characteristics of the object to be dried such as amaterial of the object to be dried or the amount of object to be dried.Drying algorithms may be different for each of the drying coursesmentioned above. The storage unit 240 may include a high-speed randomaccess memory (RAM), a magnetic disk, a static RAM (S-RAM), a dynamicRAM (D-RAM), a read-only memory (ROM), etc., but is not limited thereto.

A blowing device operation unit 250 may operate the blowing device 60 inaccordance with a control signal of the control unit 270. Specifically,the blowing device operation unit 250 may rotate the driving motor 63 inaccordance with the control signal of the control unit 270 to rotate theblowing fan 62 and the drum 20. Here, a rotation speed and a rotationdirection of the driving motor 63 may be controlled by the blowingdevice operation unit 250. When the driving motor 63 rotates by theblowing device operation unit 250, the blowing fan 62 rotates such thathumid air in the drum 20 is discharged through an air inlet, and dry,hot air is introduced into the drum 20 through the hot air outlet 45 dueto the pressure difference. Also, when the drum 20 rotates in accordancewith the rotation of the driving motor 63, the object to be dried in thedrum 20 is dried by the dry, hot air while being lifted and loweredrepetitively.

A combustion device operation unit 260 may operate the combustion device100 in accordance with the control signal of the control unit 270.Hereinafter, an embodiment of the combustion device operation unit 260will be described in detail. FIG. 11 is a view for describing acombustion device operation unit of the clothing dryer according to anembodiment. FIG. 12 is a view for describing an operation at the time ofignition of the combustion device operation unit in FIG. 11. Referringto FIGS. 11 and 12, the combustion device operation unit 260 may includea plurality of switches 271 and 276, a plurality of coils 272, 273, and274, and a variable resistor 275. A first switch 271 may be in anoff-state and a second switch 276 provided at the igniter 132 may remainin an on-state at an initial state. Here, the first switch 271 may beturned on or off in accordance with the control signal of the controlunit 270, and the second switch 276 may be turned on or off inaccordance with the temperature of the igniter 132.

When the first switch 271 is converted to an on-state in accordance withan ignition control signal of the control unit 270, voltage is appliedto a first valve coil 272, a booster coil 273, and the variable resistor275. When voltage is applied to the first valve coil 272, the firstsafety valve 123 is opened by a magnetic field generated at the firstvalve coil 272. Also, when voltage is applied to the variable resistor275, the igniter 132 is heated by resistive heat. Here, the resistancevalue of the variable resistor 275 may be controlled. When the igniter132 is heated by the variable resistor 275 and the igniter 132 reaches apreset ignition temperature, the second switch 276 is converted to anoff-state as illustrated in FIG. 12. Here, the ignition temperature isset as a temperature higher than the ignition point of gas.

When the igniter 132 reaches the ignition temperature and the secondswitch 276 is converted to the off-state, voltage is applied to a secondvalve coil 274. When voltage is applied to the second valve coil 274, amagnetic field is generated at the second valve coil 274. The secondsafety valve 124 is opened by the magnetic field formed at the secondvalve coil 274. Since the first safety valve 123 and the second safetyvalve 124 are both opened when the second switch 276 is converted to theoff-state, gas is discharged through the gas outlet 126. The dischargedgas is mixed with air in the mixing tube 131, and the gas mixed with airis ignited by the igniter 132 having a temperature higher than theignition point of the gas. Here, the output control valve 125 operatesin the high heating power mode. Specifically, the output control valve125 may maintain the first open rate and discharge gas with the maximumoutput, thus facilitating gas ignition.

The control unit 270 controls the overall operation of the clothingdryer 1. The control unit 270 may be one or more processors. Here, theone or more processors may be implemented by a plurality of arrays oflogic gates or by a combination of a universal microprocessor and amemory in which a program capable of being executed in themicroprocessor is stored. The control unit 270 may control operationunits to dry the object to be dried. The control unit 270 may operateeach configuration in accordance with a drying algorithm stored in thestorage unit 240. Specifically, the control unit 270 may operate eachconfiguration in accordance with a drying algorithm corresponding to adrying course input through the control panel 230.

In addition, the control unit 270 may control each configuration basedon a state of the clothing dryer 1 detected in the state detection unit220. Specifically, the control unit 270 may control the operation modeof the combustion device 100 based on values detected in the firsttemperature sensor 49 and the second temperature sensor 59. In addition,the control unit 270 may determine the amount of objects to be driedbased on the dryness level detected in the dryness level detection unit210, and perform a drying algorithm in accordance with the amount of theobjects to be dried. Also, the control unit 270 may analyze dryingcharacteristics of the object to be dried, and perform a dryingalgorithm in accordance with the analyzed drying characteristics of theobject to be dried. For example, the control unit 270 may determine atemperature of hot air or determine a time at which the hot air will besupplied in accordance With the drying characteristics of the object tobe dried. Hereinafter, a method of controlling a clothing dryer will bedescribed in detail with reference to FIG. 13.

FIG. 13 is a flow chart for describing an embodiment of a method ofcontrolling the clothing dryer according to an embodiment. FIG. 14 is aview for describing an air flow in a drying process of the clothingdryer according to an embodiment. Referring to FIGS. 2, 9, and 13, theuser may insert an object to be dried into the drum 20 and use thecontrol panel 230 to set a drying course at step 510. Here, the dryingcourse may be classified in accordance with the type of the object to bedried, but is not limited thereto. For example, the drying course mayalso be classified in accordance with the target dryness level,characteristics of the object to be dried, etc.

The clothing dryer 1 determines whether an operation command has beeninput from the user at step 520. When a drying command is input (YES atstep 520), the clothing dryer 1 measures the amount of the objects to bedried at step 530. Although there are no limitations to a method ofmeasuring the amount of the object to be dried, the amount of theobjects to be dried may be measured based on the dryness level detectedin the dryness level detection unit 210. For example, the amount of theobjects to be dried may be determined to be greater as the frequency ofthe current pulse generation is higher, and the amount of the objects tobe dried may be determined to be smaller as the frequency of the currentpulse generation is lower. However, measuring the amount of the objectsto be dried may be omitted when the user has input the amount of theobjects to be dried.

The clothing dryer 1 begins an ignition process at step 540.Specifically, the control unit 270 may control the valve assembly 120 todischarge gas, and apply a temperature higher than the ignition point ofthe gas to the gas being discharged to ignite the gas. Here, the valveassembly 120 may discharge the gas with the maximum output. The clothingdryer 1 begins a drying process at step 550. When the drying processbegins, the control unit 270 controls the driving motor 63 to rotate acirculation fan and the drum 20, and controls the combustion device 100to heat air. The air circulates in the drying process as illustrated inFIG. 14.

Specifically, the gas discharged from the valve assembly 120 iscombusted in the combustion chamber 41 after passing through the mixingtube 131. The air around the combustion chamber 41 is heated by thecombustion of gas. The heated air is introduced into the drum 20 alongthe rear duct 43. The air introduced into the drum as above absorbs themoisture of the object to be dried which is lifted and loweredrepetitively. The air that has absorbed the moisture is suctioned by theblowing device 60 and discharged through an exhaust tube. The pressurein the drum 20 decreases as the humid air in the drum 20 is dischargedto the outside as above, thus further accelerating the introduction ofthe air heated in the combustion chamber 41.

The clothing dryer 1 begins a cooling process at step 560. Since theobject to be dried is dried by the hot air generated in the combustionchamber 41, the temperature of the object to be dried is higher whendrying is finished. Thus, the temperature in the drum 20 should belowered through the cooling process. The control unit 270 may close thesafety valves of the valve assembly 120 to stop the combustion of gas,and drive the driving motor 63 to emit the hot air in the drum 20 to theoutside. Meanwhile, although the step 520 is illustrated in FIG. 13 asbeing performed before the ignition process, embodiments are not limitedthereto. For example, the step 520 may be performed during the ignitionprocess or the drying process.

Hereinafter, an embodiment of an ignition process will be described indetail with reference to FIG. 15. FIG. 15 is a flow chart for describingan embodiment of an ignition process in FIG. 10.

Referring to FIGS. 2, 9, and 15, the clothing dryer 1 opens the firstsafety valve 123 at step 511, and heats the igniter 132 at step 512. Asillustrated in FIG. 11, when the first switch 271 is converted to theon-state by the control command of the control unit 270, voltage isapplied to the first valve coil 272 and a magnetic field is generated.The first safety valve 123 is opened by the magnetic field generated atthe first valve coil 272. Also, when the first switch 271 is convertedto the on-state, voltage is applied to the variable resistor 275, andthe igniter 132 is heated.

The clothing dryer 1 determines whether the temperature of the igniter132 is greater than the ignition temperature at step 513. When thetemperature of the igniter 132 reaches the ignition temperature (YES atstep 513), the second safety valve 124 is opened at step 514. Asillustrated in FIG. 12, the igniter 132 reaches the ignitiontemperature, and the second switch 276 is converted to the off-state bythe igniter 132. When the second switch 276 is converted to theoff-state, voltage is applied to the second valve coil 274, and thesecond safety valve 124 is opened by the magnetic field generated at thesecond valve coil 274.

That is, gas is discharged only when both of the first safety valve 123and the second safety valve 124 are opened. The gas discharged to themixing tube 131 is mixed with air in the mixing tube 131. Here, sincethe igniter 132 has the ignition temperature higher than the ignitionpoint of the gas, the gas which is mixed with air and discharged beginsto be combusted by the igniter 132. Meanwhile, the clothing dryer 1 mayoperate in the high heating power mode at the time of ignition.Specifically, the output control valve 125 remains opened to maximizethe gas discharge amount. The clothing dryer 1 determines whether thegas ignition has succeeded at step 515. There are no limitations to amethod of determining whether the gas ignition has succeeded. Forexample, the control unit 270 may determine that the gas ignition hassucceeded when the temperature of air detected in the first temperaturesensor 49 is a preset temperature, or determine that the ignition hassucceeded as long as a gas leak is not detected by the gas sensor 133.

When the gas ignition is determined to be successful, at step 516 theclothing dryer 1 closes the output control valve 125. When the outputcontrol valve 125 is closed, the open rate of the valve assembly 120decreases, and the gas discharge amount decreases due to the decrease inthe open rate. That is, when the ignition of the clothing dryer 1 isfinished, the operation mode is changed from the high heating power modeto the low heating power mode. Meanwhile, when the gas ignition isdetermined to have failed, the clothing dryer 1 initializes the safetyvalves at step 517, and returns to the step 511 and begins the ignitionprocess again. Specifically, the control unit 270 opens the first switch271 and closes both of the first safety valve 123 and the second safetyvalve 124. In addition, since it is preferable that the gas dischargeamount be set high at the time of ignition, the control unit 270 opensthe output control valve 125 and changes the operation mode to the highheating power mode.

FIG. 16 is a view illustrating a temperature change in air when exhaustblockage has occurred. FIG. 17 is a view for describing an embodiment ofa re-ignition process. Meanwhile, the clothing dryer 1 may perform there-ignition process in the drying process. The re-ignition process maybe used in the drying process for various reasons. For example, thetemperature of the hot air supplied to the drum 20 may be excessivelyhigh and the combustion may be stopped to prevent the object to be driedfrom being damaged. The re-ignition process can be used when thecombustion is stopped as the above. In addition, the combustion may bestopped unintentionally due to exhaust blockage, etc. The control unit270 may detect an unintentional stop of the combustion due to theexhaust blockage, etc. and perform re-ignition.

For example, when a temperature value detected in the first temperaturesensor 49 drops below a combustion determination temperature F asillustrated in FIG. 16, it may be determined that the combustion hasstopped and the re-ignition process may begin. Here, the combustiondetermination temperature F may be preset. Hereinafter, the re-ignitionprocess will be described while focusing on differences with theignition process.

Referring to FIG. 17, the clothing dryer 1 initializes valve states atstep 611. Since the valve states when the combustion is finished areunclear, the control unit 270 controls the valve states to beinitialized. Specifically, the control unit 270 closes the first safetyvalve 123 and the second safety valve 124 and opens the output controlvalve 125 to control the clothing dryer 1 to operate in the high heatingpower mode. The clothing dryer 1 opens the first safety valve 123 atstep 612, and heats the igniter 132 at step 613. When the temperature ofthe igniter 132 becomes greater than the ignition temperature (YES atstep 614), the second safety valve 124 is opened at step 615. When thesecond safety valve 124 is opened, gas is discharged to the mixing tube,and the discharged gas is ignited by the igniter 132.

When it is determined that the gas ignition has succeeded (YES at step616), the clothing dryer 1 closes the output control valve 125 at step617. That is, the operation mode may be changed from the high heatingpower mode to the low heating power mode when the ignition is finished.However, the high heating power mode may be continuously maintained asneeded. Meanwhile, when it is determined that the gas ignition hasfailed, the clothing dryer 1 initializes the valve states again at step611. The clothing dryer 1 may control the valve assembly 120 to controlcombustion modes. Hereinafter, the drying process will be described indetail. FIG. 18 is a flow chart for describing in detail an embodimentof the drying process in FIG. 13. FIG. 19 is a graph illustrating achange in open rates in the drying process of FIG. 18.

Referring to FIG. 18, the clothing dryer 1 dries the object to be driedin the low heating power mode at step 621. At an initial stage ofdrying, the object to be dried contains a great amount of moisture. Whenthe object to be dried contains a great amount of moisture, the moistureof the object to be dried may be efficiently removed even whenlow-temperature hot air is used. Thus, the clothing dryer 1 may operatein the low heating power mode at the initial stage of drying, thusincreasing the gas efficiency of the clothing dryer 1.

The valve assembly 120 maintains a first open rate 01 in the low heatingpower mode as illustrated in FIG. 19 and discharges a smaller amount ofgas compared to the high heating power mode. Here, the first open rateO1 may be 50% or less of a second open rate O2. For example, the firstopen rate O1 may be 30%. Specifically, the output control valve 125maintains the on-state in the low heating power mode. When the outputcontrol valve 125 is turned on, the orifice 125 b moves forward into thegas flow passage 129. When the orifice 125 b moves forward into the gasflow passage 129, the gas flow passage 129 is closed by the orifice 125b, and the gas moves along the inner flow passage 125 c provided in theorifice 125 b. When the open rate of the gas flow passage 129 becomesthe first open rate as above, the amount of gas discharged to the mixingtube 131 also decreases, such that the heating power of the combustiondevice 100 decreases and the hot air of low temperature is generated.

The clothing dryer 1 detects the dryness level of the object to be driedat step 622. The dryness level detection unit 210 may detect the drynesslevel every predetermined period. For example, the dryness leveldetection unit 210 may count a number of operation pulses generatedduring a predetermined time (such as one minute) and calculate thedryness level of the object to be dried based on the number of operationpulses generated. The clothing dryer 1 determines whether the detecteddryness level is below the reference dryness level at step 623. When theamount of moisture contained in the object to be dried drops below apredetermined level by the low heating power mode, the object to bedried is not dried well with the hot air of low temperature. As above,the dryness level at which the object to be dried is not dried well withthe hot air of low temperature is referred to as the reference drynesslevel. The reference dryness level may be preset, and may be setdifferently in accordance with the amount of the objects to be dried andthe characteristics of the object to be dried.

When the detected dryness level is below the reference dryness level(YES at step 623), the clothing dryer 1 is converted to the high heatingpower mode at step 624. The control unit 270 opens the output controlvalve 125. As illustrated in FIG. 8, the orifice 125 b that was blockingthe flow passage moves backward toward the valve body 125 a when theoutput control valve 125 is opened. When the orifice 125 b movesbackward, the open rate of the gas flow passage 129 increases. When theopen rate of the gas flow passage 129 increases, the amount of gasdischarged to the mixing tube 131 increases, such that the heating powerof the combustion device 100 increases and hot air of high temperatureis generated.

The clothing dryer 1 detects the dryness level of the object to be driedat step 625, and determines whether the detected dryness level is belowthe target dryness level at step 626. When the detected dryness level isbelow the target dryness level (YES at step 626), the clothing dryer 1closes the safety valves at step 627. When the safety valves are closed,the gas discharge stops. Also, the clothing dryer 1 performs the coolingprocess of cooling the object to be dried. That is, the clothing dryer 1is converted to the standby mode. Here, the target dryness level refersto the dryness level at which drying is finished, and may be preset.Same as the reference dryness level, the target dryness level may alsobe set differently in accordance with the amount of the objects to bedried or the characteristics of the object to be dried. In addition, thetarget dryness level may also be set differently for each drying course.For example, the target dryness level may be set higher than that of anormal drying course when an anti-wrinkle function is selected in orderto prevent the object to be dried from being wrinkled.

Meanwhile, although it has been described in FIG. 18 that the dryingprocess is performed based on a change in the dryness level, the dryingprocess may also be performed based on time. Hereinafter, a dryingprocess performed based on time will be described with reference to FIG.20. FIG. 20 is a flow chart for describing in detail another embodimentof the drying process in FIG. 13. Hereinafter, another embodiment of thedrying process will be described while focusing on differences from thatin FIG. 18. The clothing dryer 1 dries the object to be dried in the lowheating power mode at step 631. As illustrated in FIG. 19, the outputcontrol valve 125 is turned on and the open rate of the valve assembly120 is set as the first open rate in the low heating power mode. Theclothing dryer 1 determines whether a low-temperature drying time haselapsed at step 632.

When the low-temperature drying time has elapsed (YES at step 632), theclothing dryer 1 dries the object to be dried in the high heating powermode at step 633. Here, the low-temperature drying time may be preset.In addition, the low-temperature drying time may be set differently inaccordance with the amount of the objects to be dried or the drynesslevel detected at the initial stage of drying. For example, thelow-temperature drying time may be set longer as the amount of theobjects to be dried is greater, or set shorter as the dryness leveldetected at the initial stage of drying is higher.

The clothing dryer 1 determines whether a high-temperature drying timehas elapsed at step 634. As illustrated in FIG. 19, the output controlvalve 125 is turned off and the open rate of the valve assembly 120increases from the first open rate to the second open rate in the highheating power mode. Here, the second open rate may be 100% at maximum.When the high-temperature drying time has elapsed (YES at step 634), theclothing dryer 1 closes the safety valves at step 635. That is, theclothing dryer 1 is converted to the standby mode. Here, thehigh-temperature drying time may be preset. In addition, thehigh-temperature drying time may be set differently in accordance withthe amount of the objects to be dried or the dryness level detected atthe initial stage of drying. For example, the high-temperature dryingtime may be set longer as the amount of the objects to be dried isgreater, or set shorter as the dryness level detected at the initialstage of drying is higher. In addition, the high-temperature drying timemay be set differently in accordance with the change in the drynesslevel. For example, when the change in the dryness level is great, thecontrol unit 270 may determine that the object to be dried may be easilydried and set the high-temperature drying time to be short.

Meanwhile, although it has been described in FIG. 20 that the dryingprocess is performed in accordance with a preset time, the dryingprocess may also be performed using a combination of the dryness leveland the time. For example, the clothing dryer 1 may be converted fromthe low heating power mode to the high heating power mode when one ofthe preset reference dryness level condition and the low-temperaturedrying time condition is satisfied, or converted from the low heatingpower mode to the high heating power mode when both of the referencedryness level condition and the low-temperature drying time conditionare satisfied. In addition, the high heating power mode may end when oneof the preset target dryness level condition and the high-temperaturedrying time condition is satisfied, or the high heating power mode mayend when both of the target dryness level condition and thehigh-temperature drying time condition are satisfied.

Hereinafter, an embodiment of a drying process which uses a combinationof the dryness level and time conditions will be described withreference to FIG. 21. FIG. 21 is a flow chart for describing in detailstill another embodiment of the drying process in FIG. 13. Referring toFIG. 21, the clothing dryer 1 dries object to be dried in the lowheating power mode at step 641. The clothing dryer 1 detects the drynesslevel of the object to be dried at step 642, and determines whether thedetected dryness level is below the reference dryness level at step 643.When the detected dryness level is below the reference dryness level(YES at step 643), the clothing dryer 1 dries the object to be dried inthe high heating power mode at step 644. The clothing dryer 1 determineswhether the high-temperature drying time has elapsed at step 645, andwhen the high-temperature time has elapsed (YES at step 645), theclothing dryer 1 closes the safety valves at step 646. Here, thehigh-temperature drying time may be determined by the change in thedryness level in the low heating power mode.

FIG. 22 is a view for describing another embodiment of mode change inthe drying process. Although it has been described though FIGS. 19 to 21that the drying process is classified as the low heating power modewhich generates the low-temperature hot air in accordance with the firstopen rate and the high heating power mode which generates thehigh-temperature hot air in accordance with the second open rate, themodes of the drying process are not limited thereto. That is, asillustrated in FIG. 22, the drying process may be configured of moreoperation modes. Specifically, the drying process may include a firstheating power mode which discharges gas at the open rate of 30%, asecond heating power mode which discharges gas at the open rate of 60%,and a third heating power mode which discharges gas at the open rate of100%.

Here, the valve assembly 120 may include a plurality of output controlvalves 125. For example, the valve assembly 120 may include a firstoutput control valve which lowers the open rate to 30% and a secondoutput control valve which lowers the open rate to 60%. Meanwhile,although it has been described through FIGS. 19 to 21 that the valveassembly 120 maintains the first open rate in the low heating power modeand maintains the second open rate in the high heating power mode,embodiments are not limited thereto.

In one embodiment, when a temperature detected in the first temperaturesensor 49 is greater than a first preset critical temperature, the valveassembly 120 may be controlled such that the heating power decreases.The first critical temperature refers to a temperature at which theobject to be dried may be damaged. The first critical temperature may beset differently in accordance with the type of the object to be dried.Specifically, the clothing dryer 1 may be converted from the highheating power mode to the low heating power mode when the temperature ofair introduced into the drum 20 becomes greater than the first criticaltemperature, or converted from the low heating power mode to the standbymode to prevent damage to the object to be dried.

In another embodiment, when the temperature detected in the firsttemperature sensor 49 drops below a preset second critical temperature,the clothing dryer 1 may increase the heating power. The second criticaltemperature refers to a temperature at which the drying efficiency ofthe object to be dried decreases, and may be set differently inaccordance with the type of the object to be dried. Specifically, theclothing dryer 1 may be converted from the standby mode to the lowheating power mode or the high heating power mode when the temperatureof air introduced into the drum 20 becomes lower than the secondcritical temperature, or converted from the low heating power mode tothe high heating power mode to increase the drying efficiency.

FIG. 23 is a view for describing a control for tracking a temperature.FIG. 24 is a view for describing the drying process which limits anoutput based on the temperature. In still another embodiment, theclothing dryer 1 may perform the drying process by tracking a presettemperature. Since drying is well-performed even if hot air of arelatively low temperature is supplied at the initial stage of drying,the clothing dryer 1 may operate in a low temperature mode whichmaintains a low temperature at the initial stage of drying and operatein a high temperature mode which maintains a high temperature afterdrying is performed to some extent as illustrated in FIG. 23. Theclothing dryer 1 may control a combustion mode such that hot air of apreset low temperature (such as 35° C.) is generated in the lowtemperature mode, and control the combustion mode such that hot air of apreset high temperature (such as 55° C.) is generated in the hightemperature mode. Specifically, the control unit 270 may change theoperation mode to increase the heating power when the actual temperatureof hot air is lower than a preset temperature of hot air and change theoperation mode to decrease the heating power when the actual temperatureof hot air is higher than the preset temperature of hot air, thustracking the preset hot air temperature. Hereinafter, a method oftracking the hot air temperature by controlling the operation mode willbe described in detail with reference to FIGS. 24 and 25.

Referring to FIGS. 23 and 24, the clothing dryer 1 detects a temperatureof hot air at step 711. Since the hot air generated by the combustiondevice 100 is supplied to the drum 20 along the rear flow passage 44,the clothing dryer 1 may detect the temperature of hot air using thefirst temperature sensor 49, but the method of detecting the hot airtemperature is not limited thereto. The clothing dryer 1 determineswhether the hot air temperature is lower than a first criticaltemperature t1 at step 712. The first critical temperature tl refers toa minimum maintenance temperature and may be set differently in the lowtemperature mode and the high temperature mode. For example, the firstcritical temperature tl may be set as al in the low temperature mode anda3 in the high temperature mode. When the hot air temperature is belowthe first critical temperature t1 (YES at step 712), the clothing dryer1 turns off the output control valve 125 at step 713. That is, theclothing dryer 1 converts the output control valve 125 to the off-stateand increases the open rate of the valve assembly 120 to change from thelow heating power mode to the high heating power mode. Since the gasdischarge amount increases when the operation mode is changed from thelow heating power mode to the high heating power mode, the heating powerof the combustion device 100 increases and the hot air temperature alsoincreases.

When the hot air temperature is higher than the first criticaltemperature tl (NO at step 712), the clothing dryer 1 determines whetherthe hot air temperature exceeds a second critical temperature t2 at step714. The second critical temperature t2 refers to the maximummaintenance temperature and may be set differently in the lowtemperature mode and the high temperature mode. For example, the secondcritical temperature may be set as a2 in the low temperature mode and a4in the high temperature mode. Meanwhile, when the hot air temperature islower than the second critical temperature t2 (NO at step 714), theclothing dryer 1 detects the hot air temperature again at step 711. Thatis, the clothing dryer 1 may determine that the hot air temperature iswithin a reference range and maintain the heating power. When the hotair temperature exceeds the second critical temperature t2 (YES at step714), the clothing dryer 1 determines whether the output control valve125 is open at step 715. When the output control valve 125 is determinedto be opened (YES at step 715), the clothing dryer 1 closes the outputcontrol valve 125 at step 716 and detects the hot air temperature againat step 711. That is, the clothing dryer 1 may control the outputcontrol valve 125 to be turned on and decrease the open rate. Since thegas discharge amount decreases when the open rate decreases, the heatingpower of the combustion device 100 decreases and the hot air temperaturealso drops. That is, the clothing dryer 1 is converted from the highheating power mode to the low heating power mode.

Meanwhile, when the output control valve 125 is determined to be closed(NO at step 715), the clothing dryer 1 closes the safety valves at step717, and re-ignites after a predetermined amount of time at step 718.The object to be dried may be protected by extinguishing the combustiondevice 100 as above. That is, the clothing dryer 1 is converted from thelow heating power mode to the standby mode. Meanwhile, each parameter ofthe drying process may be adjusted in accordance with a change in adried amount. Hereinafter, this will be described in detail. FIG. 25 isa flow chart for describing an embodiment of analyzing characteristicsof an object to be dried. FIG. 26 is a view for describing a change in adryness level in accordance with the characteristics of an object to bedried.

Referring to FIGS. 25 and 26, the clothing dryer 1 measures a firstdryness level at step 801. As illustrated in FIG. 26, the first drynesslevel may be measured at a first preset time Q1. The clothing dryer 1measures a second dryness level at step 802. As illustrated in FIG. 26,the second dryness level may be measured at a second preset time Q2. Theclothing dryer 1 analyzes characteristics of an object to be dried basedon the first dryness level and the second dryness level at step 803.Specifically, the control unit 270 detects a change in the dryness levelbased on the first dryness level and the second dryness level, andanalyzes the characteristics of the object to be dried. That is, adryness characteristic of the object to be dried may be analyzed. Theclothing dryer 1 adjusts parameters based on the characteristics of theobject to be dried at step 804. Here, the parameters refer to varioustypes of variables such as the above-mentioned reference dryness level,target dryness level, low-temperature drying time, high-temperaturedrying time, critical temperature, and the like which can be used forthe drying process.

For example, the clothing dryer 1 may analyze the object to be driedhaving a rapid change in dryness level such as D1 illustrated in FIG. 26as a synthetic fiber, and revise the low-temperature drying time and thehigh-temperature drying time to be shorter. In addition, since thesynthetic fiber is vulnerable to heat, the critical temperature of hotair may be set lower to prevent the synthetic fiber from being damagedby the hot air. In addition, the clothing dryer 1 may determine that theobject to be dried having a slow change in dryness level such as D2illustrated in FIG. 26 uses additional drying, and increase thehigh-temperature drying time or set the reference dryness level or thetarget dryness level to be lower.

As described above, since heating power is controlled in accordance withpredetermined open rates, gas efficiency may be increased. In addition,a valve assembly is controlled by only the predetermined open rates,thus facilitating the heating power control.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A clothing dryer comprising: a drum configured toaccommodate an object to be dried; a combustion device configured tocombust gas to heat air; a blowing device configured to transfer theheated air into the drum; and a valve assembly configured to control agas discharge amount supplied to the combustion device, wherein thevalve assembly is configured to operate in one mode among a high heatingpower mode that maximizes the gas discharge amount, a low heating powermode that generates 50% or less heating power compared to the highheating power mode, and a standby mode that blocks the gas discharge. 2.The clothing dryer according to claim 1, wherein the valve assemblyfurther comprises an output control valve configured to close a gas flowpassage to decrease an open rate.
 3. The clothing dryer according toclaim 1, further comprising: a dryness sensor configured to detect adryness level of an object to be dried; and a controller configured tocompare the dryness level detected from the dryness sensor to areference dryness level in order to control the valve assembly such thatthe operation mode of the valve assembly is changed.
 4. The clothingdryer according to claim 1, wherein the low heating power mode isconfigured to generate 30% heating power compared to the high heatingpower mode.
 5. The clothing dryer according to claim 1, furthercomprising: a temperature sensor configured to measure a temperature ofair that flows into the drum; and a controller configured to compare thetemperature measured from the temperature sensor to a referencetemperature in order to control the valve assembly such that theoperation mode of the valve assembly is changed.
 6. The clothing dryeraccording to claim 3, wherein the controller is configured to controlthe valve assembly to operate alternately between the high heating powermode and the low heating power mode.
 7. The clothing dryer according toclaim 5, wherein the controller is configured to control the valveassembly to operate alternately between the high heating power mode andthe low heating power mode.
 8. The clothing dryer according to claim 1,wherein the clothing dryer further comprises a dryness sensor configuredto detect a dryness level of an object to be dried, and determine amaintenance time of the high heating power mode based on the drynesslevel change rate detected from the dryness sensor.
 9. The clothingdryer according to claim 1, wherein the combustion device furthercomprises an igniter configured to ignite gas, and a controllerconfigured to control the valve assembly to operate in the high heatingpower mode when the igniter operates.
 10. The clothing dryer accordingto claim 9, wherein the valve assembly further comprises a safety valveconfigured to determine whether to discharge gas or not.
 11. Theclothing dryer according to claim 10, wherein the controller isconfigured to control the safety valve to be open when the temperatureof the igniter reaches an ignition point of the gas.
 12. A clothingdryer comprising: a controller configured to control an operation; adrum configured to accommodate an object to be dried; a valve assemblyconfigured to control heating power by controlling a gas dischargeamount; a combustion device configured to combust the gas dischargedfrom the valve assembly to generate hot air; and a blowing deviceconfigured to transfer the hot air into the drum, wherein the valveassembly further comprises an output control valve configured todecrease an open rate of the valve assembly to a predetermined open ratein order to control the gas discharge amount.
 13. The clothing dryeraccording to claim 12, wherein: the clothing dryer further comprises adryness level measurement device configured to measure a dryness levelof the object to be dried; and the output control valve is configured todecrease the open rate of the valve assembly to be low until the drynesslevel of the object to be dried reaches a preset reference drynesslevel.
 14. The clothing dryer according to claim 12, wherein the outputcontrol valve is configured to decrease the open rate of the valveassembly for a reference time in which a dryness level of the object tobe dried is preset.
 15. The clothing dryer according to claim 12,wherein the valve assembly further comprises a safety valve configuredto determine whether to discharge gas or not.
 16. A method ofcontrolling a clothing dryer that includes a combustion device in whichheating power is controlled by a valve assembly that controls a gasdischarge amount in accordance with a plurality of predetermined openrates, the method comprising: controlling the valve assembly to a lowopen rate among the plurality of open rates to dry an object to be driedin a low heating power mode; and when the dryness level of the object tobe dried reaches a preset reference dryness level, controlling the valveassembly to a high open rate among the plurality of open rates to dry anobject to be dried in a high heating power mode.
 17. The method of claim16, wherein controlling valve assembly further comprises closing a gasflow passage to decrease an open rate.
 18. The method of claim 16,further comprising: detecting a dryness level of the object to be dried;and comparing the dryness level detected from the dryness sensor to areference dryness level in order to control the valve assembly such thatan operation mode of the valve assembly is changed.
 19. The method ofclaim 16, wherein the low heating power mode generates 30% heating powercompared to the high heating power mode.
 20. The method of claim 16,further comprising: measuring a temperature of air that flows into adrum; and comparing the temperature measured from the temperature sensorto a reference temperature in order to control the valve assembly suchthat the operation mode of the valve assembly is changed.